Structural evolution in the neutron-rich nuclei ¹°6Zr and ¹°8Zr.

The low-lying states in ¹°6Zr and ¹°8Zr have been investigated by means of ß-γ and isomer spectroscopy at the radioactive isotope beam factory (RIBF), respectively. A new isomer with a half-life of 620 ± 150 ns has been identified in ¹°8Zr. For the sequence of even-even Zr isotopes, the excitation energies of the first 2⁺ states reach a minimum at N = 64 and gradually increase as the neutron number increases up to N = 68, suggesting a deformed subshell closure at N = 64. The deformed ground state of ¹°8Zr indicates that a spherical subshell gap predicted at N = 70 is not large enough to change the ground state of ¹°8Zr to the spherical shape. The possibility of a tetrahedral shape isomer in ¹°8Zr is also discussed.

ß-decay half-lives of very neutron-rich Kr to Tc isotopes on the boundary of the r-process path: an indication of fast r-matter flow.

The ß-decay half-lives of 38 neutron-rich isotopes from (36)Kr to (43)Tc have been measured; the half-lives of (100)Kr, (103-105)Sr, (106-108)Y, (108-110)Zr, (111,112)Nb, (112-115)Mo, and (116,117)Tc are reported here. The results when compared with previous standard models indicate an overestimation in the predicted half-lives by a factor of 2 or more in the A≈110 region. A revised model based on the second generation gross theory of ß decay better predicts the measured half-lives and suggests a more rapid flow of the rapid neutron-capture process (r-matter flow) through this region than previously predicted.

New dopaminergic and indoleamine-accumulating cells in the growth zone of goldfish retinas after neurotoxic destruction.

Juvenile goldfish were allowed to grow for 3 months after dopaminergic or indoleamine-accumulating cells in their retinas had been destroyed by intravitreal injection of 6-hydroxydopamine or 5,7-dihydroxytryptamine, respectively. New cells of each type were found growing in concentric rings at the margin of the retina. To compensate for the loss of dopaminergic innervation in retinas treated with 6-hydroxydopamine, cells in the growth zone appeared to proliferate at a higher rate than those in untreated retinas and long processes were extended into the retina by the first dopaminergic cells to appear.

Determination of a localized surface plasmon resonance mode of Cu7S4 nanodisks by plasmon coupling.

Plasmon properties such as peak position, extinction cross-section and local electric field intensity are strongly dependent on excited, localized surface plasmon resonance (LSPR) modes. In non-spherical copper chalcogenide nanoparticles, assignment of the LSPR peaks to the corresponding oscillation modes has been controversial and requires experimental verification. We determined the in-plane LSPR mode of roxbyite Cu7S4 nanodisks from the plasmon coupling effect of nanodisks in solution. Compared with individual Cu7S4 nanodisks, self-assembled Cu7S4 nanodisk arrays in chloroform exhibited a blue-shifted LSPR peak with weaker optical density. This strongly suggests that the singular LSPR peak in the near-infrared region mainly originates from the in-plane oscillation mode. In addition, we demonstrate that the same LSPR peak can be readily tuned by controlling the number of disks in the array.

Embryonic development of monoaminergic neurons in the chick retina.

By means of a histofluorescence technique, embryonic and postnatal development of monoaminergic neurons was followed in the chicken retina with or without intravitreal injection of monoamines 30-60 minutes before eye removal. Fluorescent cells were tentatively classified into five subsets with respect to the soma shape, localization, migration of somata during retinal development, uptake capacity (color and intensity in fluorescence), and sensitivity to neurotoxins. The five subsets of cells were endogenous dopaminergic (DA), catecholamine-accumulating (CA), indoleamine-accumulating (IA), CA-bipolarlike, and IA-bipolarlike cells. Greenish endogenous DA-cells first appeared at the 14-15th embryonic day. The cell body of DA-cells was initially fusiform and located slightly distal to the innermost level of the inner nuclear layer (INL). They became round or oval and migrated to the innermost level of the INL by day 20. Both large and small bottle-shaped CA-cells were visualized at an intermediate portion of INL by intravitreal injection of exogenously applied dopamine or noradrenaline (1-2 micrograms/eye) at day 10. Large bottle-shaped cells, like the DA cells, changed to round or oval and migrated to the innermost level of the INL by day 20. On the other hand, small bottle-shaped CA-cells retained their cell shape and location in the INL as retinal development progressed. Therefore, the large bottle-shaped CA-cells seen in an early developmental stage correspond to the DA-cells. IA-cells were visualized one or two cell rows outward in the INL first at day 13-14 by intravitreal injection of 5,6-dihydroxytryptamine or 5-hydroxytryptamine (1-5 micrograms).(ABSTRACT TRUNCATED AT 250 WORDS)

Malformation in infants of mothers with epilepsy receiving antiepileptic drugs.

To assess the relative contribution of antiepileptic drugs (AEDS) to occurrence of congenital malformations, we compared two prospective studies. We analyzed data for 14 AEDs for total daily doses (drug score) and eight background factors. From the first study, the drug score and polytherapy--particularly the use of valproate plus carbamazepine--were suspected to be primary factors for increased incidence of congenital malformation. In the other study, the drug score for each case was decreased, and polytherapy--particularly valproate plus carbamazepine--was changed to monotherapy before conception. These changes significantly decreased the incidence of malformations. Among risk factors, only the doses of methylphenobarbital for mothers of infants with malformations were significantly higher than those for mothers of infants without malformations. Statistical differences were seen in drug score, number of AEDs, maternal age at delivery, seizure type, and etiology of epilepsy between the two groups. When data were corrected for seizure type, maternal age at delivery, or etiology of epilepsy, the difference in the incidence of malformations did not disappear, but it did disappear when data were corrected for drug score or number of AEDs. These results support our previous observations that AEDs are primary factors for the increased incidence of congenital malformation in infants of mothers with epilepsy.

Double-staining of horizontal and amacrine cells by intracellular injection with lucifer yellow and biocytin in carp retina.

Horizontal and amacrine cells in the isolated carp retina were impaled with micropipette electrode, identified by their characteristic light responses, and injected iontophoretically with markers for morphological study. Both Lucifer Yellow CH and biocytin were injected simultaneously. Lucifer Yellow was seen by its own fluorescence while biocytin was visualized by binding with Texas Red-linked or horseradish peroxidase-conjugated avidin. For cone-connected horizontal cells, biocytin-coupled cells were found to be approximately five-times more numerous than Lucifer Yellow-coupled cells. Coupling for both tracers was consistently hampered by intravitreally applied dopamine. In untreated retinas, the injected Lucifer Yellow was restricted within one rod-connected horizontal cell, while biocytin revealed several coupled neighbors. Amacrine cells, labeled by the tracers, were morphologically grouped into eight types, based on our earlier classification. Among them, amacrine cells, belonging to three types (Fnd, Pmb or Pma), were confirmed to be Lucifer Yellow-coupled, and the number of biocytin-coupled cells was more numerous (about 2.5 times) than that of Lucifer Yellow-coupled cells. Most amacrine cells (i.e. Pwd, Fnb and Fna) showed biocytin-coupling with no Lucifer Yellow-coupling. A few classified (i.e. Pwb and Fwa) and unclassified cells did not show any coupling. Since the tracer coupling takes place via gap junctions, the majority of amacrine cells, belonging to certain homologous types, appear to be functionally coupled with each other in the inner plexiform layer. However, dopamine did not influence the range of tracer coupling between amacrine cells in the carp retina under the present experimental conditions.

Functional and morphological correlates of amacrine cells in carp retina.

Experiments were conducted on isolated retinas of adult carp (Cyprinus carpio) to investigate correlations between photoresponses and morphological features of amacrine cells. The fluorescence dye Lucifer Yellow CH was iontophoretically injected into single cells which had been characterized electrophysiologically. Photoresponses were classified into two main types (transient ON-OFF and sustained), which were further subgrouped into "fast" and "slow" ON-OFF types and into ON-center and OFF-center types, respectively. In the spectral response curve, all the types dealt with showed a maximum response at 621 nm, indicating that main input signals derive from red-sensitive cones. The cells marked by intracellular injection of the dye showed a great variety in morphology. Cells were classified into 8 subtypes, based on soma shape (fusiform or pyriform), dendritic field area (narrow, less than 0.3 mm2; medium, 0.3-0.8 mm2; wide, greater than 0.8 mm2), and dendritic stratification in the inner plexiform layer (restricted to sublamina a or b, or distributed diffusely). In certain cases a given response type was correlated with a specific morphological type, while receptive field size was not strictly correlated with dendritic field areas. Long and fine peripheral "axon-like" processes were found to arise from the primary dendrites of most fusiform cells. Dye-coupling was found among cells which appear to belong to the same cell category.

Dendritic morphology of indoleamine cells revealed by intracellular injection of lucifer yellow in fixed carp retina.

The dendritic morphology of indoleamine amacrine cells in carp retina was investigated by identifying their fluorescent cell bodies by preloading with noradrenaline followed by iontophoretic injection of Lucifer Yellow in isolated and aldehyde-fixed preparations under microscopic control. Although two subpopulations of serotonin-like immunoreactive amacrine cells (small and large in soma size) were found, small cells were not seen in aldehyde-fixed preparations. Cells preloaded with noradrenaline corresponded to large immunoreactive cells and were labeled with Lucifer Yellow. The cell bodies labeled were located at the innermost level of the inner nuclear layer, and gave rise to three to five primary dendrites which branched frequently and were found mainly in sublamina a of the inner plexiform layer. These cells examined in an intermediate region between the optic disc and the retinal periphery were pyriform in soma shape while dendritic fields were found or oval covering an area of 0.18 +/- 0.05 mm2 (510 +/- 80 microns in diameter). Cell density in this region was about 32 cells/mm2 and, therefore, their dendritic field coverage was approximately 6.0.

Dendritic morphology of dopaminergic cells revealed by intracellular injection of Lucifer yellow in fixed carp retina.

The dendritic morphology of dopaminergic cells in carp retinas was investigated by identifying their fluorescent cell bodies in isolated, aldehyde-fixed preparations and injecting them iontophoretically with Lucifer yellow CH (LY) under microscopic control. The LY-injected cells were examined in flatmount and in radial cryosections. The cell bodies were located at the inner margin of the inner nuclear layer (the amacrine cell sublayer), and gave rise to 3-5 primary dendrites that branched repeatedly within the inner plexiform layer to form a narrow-field, diffusely branched dendritic tree. In some cases, a distal process was found to extent to the outer plexiform layer, representing the interplexiform type of cells. The 59 filled cells had roughly round or oval dendritic fields covering an area of 0.102 +/- 0.003 mm2 (361 +/- 57 micron in diameter) in the intermediate retinal region. The density of dopaminergic cells in this region was 31 cells/mm2 and, therefore, the dendritic field coverage of these cells approximately 3.0.

Regional difference in the dendritic morphology of dopamine cells in carp retina.

The dendritic morphology of dopamine (DA) cells in the inner plexiform layer of the retina of carp (body length, ca. 33 cm) was investigated by identifying their fluorescent cell bodies in isolated, aldehyde-fixed flat-mounts and injecting them iontophoretically with Lucifer yellow CH under microscopic control. Attention was paid to clarifying regional differences in their dendritic morphology. In the marginal zone within 0.25 mm from the retinal edge, the density of DA cells was extremely high (120 cells/mm2), their dendrites tended to extend in parallel with the retinal circumference, and the dendritic field size was small (2.5 X 10(-2) mm2). As the injection point was shifted centrally by steps, the dendrites of DA cells tended to extend toward the optic disc and subsequently toward the margin, finally forming a round or oval dendritic field for each cell. Concomitantly with such changes in the dendritic field, the cell density sharply decreased to about 30 cells/mm2, and the dendritic field size increased to 10 X 10(-2) mm2 in a zone 2-3 mm interior to the margin. However, the dendritic coverage factor was consistently about 3.0 over the entire retinal field. Such morphological changes observed sequentially from the retinal margin to the intermediate region represent a developmental course of DA cells in the carp retina.

Sequential course of uptake of intravitreal 5,7-dihydroxytryptamine by carp retinal cells.

The sequential course of uptake by retinal cells of intravitreally injected 5,7-dihydroxytryptamine (5,7-DHT) together with dopamine (DA) was investigated in juvenile carp retinas, which were removed at various intervals (1-24 h) after injection. The cells taken up 5,7-DHT were visualized immunohistochemically with anti-serotonin (5-HT) antibody and FITC-conjugated IgG. After a mixture of 5,7-DHT and DA (2.5, 10 or 20 micrograms each) was given, large-sized indoleamine (IA) amacrine cells first (1-4 h), and then small-sized indoleamine-accumulating amacrine amacrine (IAA) cells (4-12 h), bipolar cells (8-12 h) and in some cases photoreceptor cells (12-24 h) were sequentially observed, and finally the immunoreactive structures almost disappeared around 24 h after injection. When the mixture of 5,7-DHT and DA (10 micrograms each) was injected into the eyes of reserpinized fish, the same sequential uptake of 5,7-DHT was seen in a faster time course, but additionally various classes of retinal cells (horizontal, ganglion and Müller cells) became visible as irregular clusters. However, DA cells were never visualized at any stages of all the experiments, indicating that DA cells do not take up 5,7-DHT in the carp retina, which was further confirmed by double labeling of 5-HT- and tyrosine hydroxylase-like immunoreactive cells. Double labeling also revealed that 5,7-DHT-accumulating bipolar cells appear to represent a subclass different from that of protein kinase C-like immunoreactive bipolar cells.

Development of retinal monoamine neurons in larval goldfish: a histofluorescence study.

The emergence of retinal monoamine neurons was explored in embryonic and larval goldfish (Carassius auratus) by means of a histofluorescence technique. The high-affinity uptake capacity of dopamine (DA) and indoleamine-accumulating (IA) neurons for exogenously applied DA and 5,6-dihydroxytryptamine began to occur simultaneously on the hatching day (stage 25/26). Endogenous DA neurons were first detected on the third postnatal day (stage 26/27). The appearance of DA and IA neurons was found to begin in the central part and to extend to the peripheral part of individual retinas. The first DA and IA neurons to be detected were situated in the inner nuclear layer and migrated proximally to the innermost level of the inner nuclear layer 5-7 days after hatching. The developmental process of monoamine neurons observed represents an aspect of cellular differentiation and maturation in the goldfish retina.

L-Glutamate depolarizes ON-OFF transient type of amacrine cells in the carp retina: an ionophoretic study.

Amacrine cells generating the ON-OFF transient type of photoresponse, which is most frequently encountered, were identified by intracellular recording and staining with a fluorescent dye Lucifer Yellow in the carp (Cyprinus carpio) retina. L-Glutamate applied ionophoretically slowly depolarized the amacrine cells by about 10 mV and reduced their photoresponses during the application. Such changes gradually recovered following the cessation of L-glutamate injection. The results indicate that this amino acid directly activates the ON-OFF type amacrine cells.

Opposite effects of ammonia and carbon dioxide on dye coupling between horizontal cells in the carp retina.

Effects of ammonia (NH3) and carbon dioxide (CO2) on the membrane potential of horizontal cells and on dye coupling between the cells in isolated retinas of the carp (Cyprinus carpio) were investigated. Ammonia (less than 300 ppm NH3 in air) initially depolarized and subsequently hyperpolarized, while CO2 (10% in air) hyperpolarized the membrane potential of horizontal cells, accompanied by a diminution of both center and surround responses to spot and annular light stimuli. During the course of amplitude diminution, the center response consistently became smaller with NH3 and larger with CO2 than the surround response. In the presence of intravitreally applied DA (50 microM) or amphetamine (100 microM), a fluorescent dye Lucifer Yellow CH (LY) was found to be restricted to single injected horizontal cells. The presence of intravitreal haloperidol (100 microM) for 20-25 min or an exposure of the retina to NH3 for 5-10 min diffused the restricted LY from single injected cells to numerous neighboring cells. On the other hand, CO2 was found to restrict the injected dye to single cells, an effect similar to that of DA and opposite to that of NH3 and haloperidol. The results suggest that NH3 appears to act as a coupler while CO2 acts as an uncoupler on gap junctions between horizontal cells in the carp retina, presumably by changing the intracellular pH. In addition, a brief exposure of cells, marked with LY in the presence of DA, to the exciting light 426 nm was found to prevent the NH3-induced dye diffusion from single cells to their neighbors; the reason is unknown.

Spatial orientation of horizontal cell axon terminals in the carp retina.

In flatmounts of the carp (Cyprinus carpio) retina, 646 horizontal cells were singly marked by intracellular Lucifer yellow CH (LY) in the presence of dopamine or amphetamine, agents which were useful for restricting LY to single injected cells. Most axon terminals of cone-connected horizontal cells have a tendency to orient either radially or tangentially in the retinal field with respect to the optic disc as a center. Although the fluorescent cellular (dendritic field) area greatly varied depending upon the cell type (L-, RG- and YRB-type), the lengths of the axonal processes (axon plus terminal) were all comparable (400-600 microns). A few cells (4.1% of cells with visible axons) possessed a bifurcate axon with two axon terminals. Axons were not observed on rod-connected horizontal cells. The cellular area and the axonal length of L- and RG-type cells appeared to be smaller in the central than in the intermediate region of the retinal field.

Retinal growth in carp of the same age: density and number of dopamine neurons.

Research has shown that an increase in the size of retina with fish growth is accompanied by a reduction in the density of monoamine neurons along with an increase in their cell number per retina. The age of fish, however, has not been considered in relation to the above. In the present study, juvenile carp (6.4 +/- 0.7 cm in body length), hatched 2 months earlier, were reared for 10 months under 2 different sets of conditions; one group was kept in a small aquarium at room temperature (RT, 9-26 degrees C), and the other was kept in a large aquarium in which the water temperature was constant (CT, 22 degrees C). The left eye of fish transferred into the RT aquarium was intravitreally injected with 5,7-dihydroxytryptamine (5,7-DHT; 1.0 microgram) to destroy indoleamine-accumulating (IA) neurons. The fish grew faster in the CT (16 +/- 1.6 cm) than in the RT aquarium (9.3 +/- 1.7 cm), resulting in a wide variation among fish of the same age. In fluorescent retinal flatmounts, the density of dopamine (DA) neurons was found to be lower, but their cell number per retina greater in the CT than in the RT group; these differences were statistically significant (P less than 0.001). The data suggest that the above parameters depend on the size of carp but not on their age. In the fish treated with 5,7-DHT and reared in the RT aquarium for 10 months, the growth zone of the retina was determined by circumferential addition of IA cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth rate of a peripheral annulus defined by neurotoxic destruction in the goldfish retina.

Fifteen goldfish of similar size (6.8 cm in body length on the average) were reared in an aquarium (about 22 degrees C) for 5 months after neurotoxic destruction of retinal dopamine (DA) cells with intravitreal injection of 6-hydroxydopamine, and then further for 8 months after destruction of indoleamine-accumulating cells with 5,7-dihydroxytryptamine. By means of a histofluorescence technique for retinal wholemounts, the growth rate and the number of DA cells were estimated for a peripheral annulus which had been well defined by the successive neurotoxic destructions of monoamine-accumulating cells. As the fish grew from 8.4 to 11.6 cm in body length on the average over the 8-month period, the defined peripheral annulus of the retina was found to be enlarged radially by approximately 1.5 X and circumferentially by 1.3 X while the number of DA cells in the annulus remained unchanged.

Paradoxical induction of dopaminergic cells following intravitreal injection of high doses of 6-hydroxydopamine in juvenile carp retina.

Histofluorescence studies were conducted on two groups of juvenile carp (body length, 12.7 and 6.6 cm on the average, respectively) during certain periods (3-11 months) of retinal growth, to evaluate the destructive effect of 6-hydroxydopamine on dopaminergic and indoleamine-accumulating cells. Within a certain range of doses (0.1-5.0 micrograms/eye) of the neurotoxin injected intravitreally, it was found to destroy both classes of cells in a dose-dependent manner: more cells disappeared with higher doses. However, a high dose (5-25 micrograms/eye) of the neurotoxin caused paradoxical events in the retina, inducing an appearance of clustered dopaminergic cells with various soma sizes and abnormally high regional density, disturbed laminar organization, and a facilitated growth rate at the retinal margin. A preliminary examination with [3H]thymidine labelling suggests that the high dose of 6-hydroxydopamine may cause severe damage to certain classes of cells including dopaminergic and indoleamine-accumulating cells, and that a metamorphic change of precursor cells (neuroblasts) in the outer nuclear layer is responsible for the induction of such abnormal dopaminergic cells as clusters.

Dual actions of some amino acids on spike discharges in the carp retina.

The effects of some amino acids (Glu, Gly and GABA), applied in 3 different manners (electrophoretically, in the superfusate and by pressure-microinjection), were investigated on spontaneous and light-induced spike discharges in the isolated carp retina. When applied electrophoretically or by pressure-microinjection in the inner plexiform layer (IPL), the agents acted directly on spike-generating units. Electrophoretic application of Glu at IPL consistently increased while Gly and GABA always decreased spike discharges regardless of the light-induced response patterns, when the tangential distance between the recording and injection electrodes was 25--100 micron. Increasing the distance up to 400 micron diminished the effects, but did not invert them. When added to the superfusate, the amino acids produced a dual action (two different sequential effects); Glu (5 mM) initially decreased and increased spike discharges, while Gly and GABA (5 mM) produced opposite effects. Gly and GABA tended to suppress selectively off-discharges (of ON--OFF units and certain OFF-center units), leaving on-discharges (of ON--OFF units and certain ON-center units) unaffected. The amino acids produced different effects on some units, when applied by pressure-microinjection into OPL or IPL. When injected in OPL Glu suppressed, while in IPL it activated spike discharges, whereas Gly and GABA caused opposite changes to those observed with Glu. Therefore, the action of the agents when pressure-microinjected in OPL is equivalent to the initial action of the agents applied in the superfusate. The dual actions of the agents are assumed to be mediated by bipolar cells, resulting in disfacilitation (Glu) or in disinhibition (Gly or GABA) of spike-generating units.